EPA 609 System Evacuation & Recharging Procedures

Question 1

What is the main purpose of evacuating (pulling a vacuum on) an MVAC system before recharging?

Accepted Answer

To remove air and moisture from the system

Answer

Evacuation removes non-condensable air and boils off moisture. Moisture can form acids and freeze at the expansion device, and air raises operating pressures and reduces cooling.

Question 2

Why does applying a deep vacuum help remove moisture from an MVAC system?

Accepted Answer

Lower pressure lowers water's boiling point, so it evaporates and is pulled out

Answer

As pressure drops, the boiling point of water drops too. Under a deep vacuum, moisture boils at ambient temperature and the vacuum pump pulls the vapor out.

Question 3

What is the most accurate way to recharge an MVAC system with refrigerant?

Accepted Answer

Charge by weight to the amount on the vehicle's specification label

Answer

Modern systems hold small, precise charges. Weighing in the exact amount given on the under-hood label or in service information is the only reliable way to get the charge right.

Question 4

After the vacuum pump is shut off, the gauge shows the vacuum rising (pressure increasing) within a few minutes. What does this most likely mean?

Accepted Answer

There is a leak or remaining moisture in the system

Answer

In a vacuum decay test, a properly sealed, dry system holds its vacuum. If the vacuum rises, air is leaking in or trapped moisture is still boiling off, so the system should not be charged until the cause is fixed.

Question 5

What is a likely result of overcharging an MVAC system with refrigerant?

Accepted Answer

Excessive high-side pressure, poor cooling and possible compressor damage

Answer

Too much refrigerant raises head pressure, reduces cooling efficiency and can cause liquid slugging, which damages the compressor. It may also trip high-pressure safety switches.

EPA 609 - EPA Section 609 Refrigerant Certification Practice Test

EPA 609 - EPA Section 609 Refrigerant Certification Practice Test

EPA 609 System Evacuation & Recharging Procedures